Multipole

From a single charge goes out a monopole field. An example of this is the electric field of an electron.

However, as soon as two poles, or two oppositely charged particles, are present, one speaks of a dipole field. Examples include magnets with a south pole and a north pole.

As soon as there are several charge distributions, we talk about Multipoles. In general, it describes the structures of the magnetic and electric fields resulting from the charge distribution.

The electric field present at a point charge is, for example, a monopole field, while a magnetic field is always at least one dipole field. If it is a multipole field, then the multipole moment in the magnetic field is the dipole moment which is lowest and does not vanish.

The compulsive dipole structure of magnets is also the reason why permanent magnets always have at least two poles - there is no magnet that has only one pole.


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